Offshore deep drilling method from a floating platform



4 Sheets-Sheet 1 K. M. NICOLSON OFFSHORE DEEP DRILLING METHOD FROM AFLOATING PLATFORM 31. 1956 Sept. 12, 1967 Filed Dec.

Sept. 12, 1967 K. M. NICOLSON OFFSHORE DEEP DRILLING METHOD FROM AFLOATING PLATFORM 31 J 1956 4 Sheets-Sheet 2 Filed Dec.

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/ATToRNEYs INVENTOR KINGSLEV M. N/COLSON Sept. 12, 1967 OFFSHORE DEEP K.M. NICOLSON 3,341,398 DRILLING METHOD FROM A FLOATING PLATFORM FiledDec. 31 1956 4 Sheets-Sheet 4 K/NGSLEV M. N/COLSON United States Patent3,341,398 OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORMKingsley M. Nicolson, Fullerton, Califi, assignor, by

mesne assignments, to Chevron Research Company, a

corporation of Delaware Filed Dec. 31, 1956, Ser. No. 631,715 3 Claims.(Cl. 175-7) The present invention relates to a method of drilling from afully floating platform. More particularly, the invention relates to amethod of drilling a vertical well bore into the underwater bottomwhether or not the bottom is steeply dipping from a fully floatingplatform.

It is a particular object of this invention to provide a method ofdrilling a vertical well bore into an underwater bottom from a fullyfloating vessel without requiring a template or other guiding means forspudding in the well bore by suspending a drill string from the deck ofa fully floating vessel with a substantial portion thereof held intension when the lower end thereof including a drill bit and a weightedportion of said drill string touches bottom. Then, with only theweighted portion of the drill string exerting thrust on the drill bitthe drill string is rotated from the working deck of the vessel. Theborehole is spudded in vertically by drilling ahead with the drill bituntil a consolidated rock bed or other competent formation is drilledinto. Then, at least one conductor pipe is cemented in the boreholebefore the drill string is disconnected from the borehole.

Another object of the present invention is to provide a method fordrilling into an underwater bottom from a fully floating platformwithout danger of contaminating the body of water with oil or gasencountered in the well bore by establishing pressure control over theborehole with a well head on bottom before the borehole penetratespotential reservoir formations. In carrying out the method, such wellhead is set on bottom with all work performed on the working deck of thefloating vessel by maintaining continuous engagement between theunderwater bottom and the floating vessel after the drill string hasbeen first spudded without templates or other means for guiding the bitinto the bottom. In said preferred method of carrying out the invention,an assembled conductor pipe is lowered into the vertical borehole formedin the underwater bottom by the drill bit, but penetration thereinto islimited by assembling a landing flange to the upper end of said pipebefore it is lowered. The conductor pipe is then cemented in positionthrough a drill string extending from the deck of the floating vesselinto the borehole; said cementing being performed after a guide assemblyis lowered on at least a pair of guide cables so that it slides downalong the drilling string extending downward from the working deck intothe borehole. The guide assembly is latched to the conductor pipe abovesaid landing flange. Following cementing of the conductor pipe andsecuring of the guide cable assembly to said conductor pipe, theinterconnection between the drill string and the floating vessel isbroken and the guide cables slacked to permit cement around saidconductor pipe to set without vertical force being applied to it throughthe vessel moving under wind and tide action. Pressure controlequipment, including at least one blow out preventer assembly is thenlowered along the guide cables after they are again drawn taut betweenthe well head and the floating vessel. Said pressure control equipmentis desirably coupled to the top of the conductor pipe by a safety jointor other quick-connect joint that requires less than one full rotationof the pressure control means, guide lines or said conductor pipe.

In the drilling of well bores to explore for oil, gas and the likethrough deep waters, it is necessary either to 3,341,398 Patented Sept.12, 1967 build a platform extending from the ocean bottom to a levelwell above the water surface or to drill from a floating platform. It isof course uneconomical to build large fixed platforms unless there is ahigh probability of finding oil. Accordingly, it is desirable to be ableto drill a well bore from a mobile platform such as a floating platform.The greater mobility of a fully floating platform makes this type ofdrilling more attractive than platforms that have a floating foundationpartly submerged by vertical anchors. While such restrained floatingplatforms provide easier drilling conditions, the cost of verticalanchors makes their use economically unattractive.

While in general it has been proposed to anchor a vessel over a drillingsite and then drill into the underwater bottom with conventional rotaryequipment, such underwater bottoms are seldom level and hard so thatadequate pressure control equipment can be set directly on bottom. Thefunction of such pressure control equipment is to maintain hydrostaticpressure in the well bore that will always be greater than that of anygas or oil encountered therein. Loss of such pressure control is knownas a blow out. The problem of blow outs is of course a serious one fromthe standpoint of explosion and fire hazards in land operations. It iseven more serious in offshore operations, such as those along theCalifornia coast, where any release of oil or gas could contaminate theocean so that marine life is destroyed and the adjacent resort beachesruined. Accordingly, it is considered imperative that adequate andcomplete Well head control equipment be established before drilling ispermitted in an underwater bottom where contamination of the water ispossible.

It has been suggested heretofore that well head controls be located onthe working deck of the drilling vessel to give easy access formaintenance and to assure its recovery when drilling is completed. Inthis system, a conductor pipe runs from the well bore up to the controlequipment located on the deck of the surface vessel. This of courserequires that the conductor pipe be flexible enough to permit lateraland vertical movement of the surface vessel while drilling. One seriousproblem in using pressure controls at the deck is that the wind and tideforces on the vessel can put an undue strain on the conductor pipe. Suchstrain, of course, makes the conductor pipe more susceptible to damagethat can result in complete loss of well head control. For thesereasons, it is desirable to position the well head control equipment onthe bottom. However, the pressure control equipment is quite expensiveand therefore it is desirable that it be possible to retrieve it afterthe well is drilled.

While it has been suggested heretofore that well head control equipmentbe placed on bottom, the method of initiating, or spudding-in theborehole, landing of conductor pipe and control equipment, as well asretrieving this equipment as practiced heretofore frequently requiredthe aid of a human diver, or other auxiliary equipment not forming partof the normal drilling equipment. The cost of diver service, in additionto rig time (i.e., rental charges on drilling equipment, drill crewwages, etc.), makes these operations unusually expensive. In general,the cost of a diver service alone may run as high as $800 to $1,000 perday. Additionally, the time that a diver can operate, even in shallowwater, is greatly limited by human, physical endurance. In deep waters,it is not feasible to use a diver even if one is required. Additionally,in water bottoms having a thick bed of unconsolidated sediments, diverservice cannot be used Without difficulty.

For the foregoing reasons, it is necessary and desirable that there beprovided a system for drilling a vertical borehole into an underwaterbottom irrespective of its slope or hardness and to a depth so that aconductor pipe can be set and cemented in a competent formation with atleast an upper portion thereof extending above bottom to receive wellhead or pressure control equipment. (In this sense, competent means anearth formation, such as a consolidated shale bed, having sufficientcompaction to give it strength and being impermeable so that the pipecan be bonded to it with cement.)

In accordance with a preferred method of carrying out the presentinvention, a drill bit is assembled on the lower end of a conductor pipeor surface pipe having a predetermined weight. The drill bit andconductor pipe are then connected to a drill string through averticallyreciprocable connection; said drill string in turn is rotatedby a gimbaled rotary table positioned below a supporting drill derrickmounted on the working deck of the fully floating platform. Thevertically-movable connection permits the entire string to hang freelyas a pendulum below the vessel so that even in deep waters only thepredetermined weight of the conductor pipe is imposed on the drill bitwhen the bit first touches bottom. Then without further guiding thereof,the drill bit is rotated with only said predetermined weight thereon andwith a substantial portion of the drill string in tension duringspuddingin. By such rotation and holding said drill string in tensionabove the weighted section the bit and drill string is maintainedvertical even on very steeply dipping bottoms. Drilling then continuesuntil the borehole is deep enough to receive the full length of theconductor pipe. A landing flange otherwise serving as a feeler forbottom indicates when the conductor pipe has been drilled deep enoughinto the bottom. Desirably, this depth is preselected so the conductorpipe will be sufficiently long to assure its penetration into acompetent formation. After the landing flange has engaged bottom withthe conductor pipe attached thereto and extending into the borehole,cement is supplied to the annular space between the conductor pipe andthe borehole while connection between the drill string and borehole ismaintained. Desirably, this is done without removal of the drill stringfrom the well bore. Alternatively, the conductor or surface pipe may becemented in the borehole using a cement string guided into the landedconductor pipe through a guide assembly lowered on at least a pair ofcables along the drill string while said drill string is still in thewell bore. In either method of cementing, said guide assembly is loweredto slide down along the drill string while said string is still in theborehole and to establish a continuity of connection between the deck ofthe drilling vessel and the conductor pipe in the borehole before cementis injected. This continuity of interconnection between vessel andborehole just prior to the cementing operation is particularly essentialto eliminate human diver service.

When the guide assembly, which desirably includes an enlarged funnelused to guide well head pressure control equipment into engagement withthe conductor pipe, has been landed and interconnected, the drill stringis disconnected from the borehole immediately above the landing flange.Then, the guide cables are released so that cement between the conductorpipe and the borehole may set without danger of the conductor pipe beingpulled up by the cables due to action of wave and tide forces on thedrilling vessel. Said conductor pipe not only serves to prevent sluflingof the underwater sediments into the well bore, but also provides a firmvertical anchor for blow out prevention equipment connected thereto asdrilling proceeds below the cemented section of the conductor pipe downinto potential oil and gas-bearing formations.

After said conductor pipe has been cemented in the borehole inaccordance with the invention, drilling proceeds to a greater depththrough blow out prevention equipment, and other well head controlequipment, coupled directly to the conductor pipe. Such well headequipment is assembled to the conductorpipe by again tightening theguide cables and lowering it along them. Final assembly of said wellhead equipment to the conductor pipe is desirably made through aquick-connect joint, otherwise known as a safety joint, which permits afluidtight connection without requiring rotation of the guide cables,blow out preventer, drilling head or other equipment that guidablyslides down along the cables. In particular, this equipment is notrotated so that thecontrol hydraulic lines and the drilling fluid returnlines will not become twisted during assembly. Thus, the hydrauliccontrol means for remotely operating the well head equipment from thevessels deck can be connected prior to lowering of said equipment alongthe guide cables. At the same time, said guide cables are held nearlystraight and vertical between the borehole and the drilling vessel.After assembly of said well head equipment and the drilling head,drilling proceeds by guiding a drill bit and the drill string along theguide cables and into the drilling head assembly and the borehole.

The drilling operation then proceeds under full pressure control of thewell bore. This, of course, includes the use of drilling fluid thatreturns to the working deck through a mud return line connected to theborehole at a point intermediate the blow out prevention equipment andthe drilling head. Upon completion of drilling, it is desirable toabandon said borehole, but prevent any possible seepage or other escapeof oil or gas by setting a cement plug in the well bore of sufficientlength to bond both to the uncased portion of the borehole and at leastpart of the cased section of the borehole. Such abandonment will ofcourse occur where it is decided that production cannot be established,or for other reasons, it is not desired to complete a producing wellthrough this particular borehole. After cement has been spotted in thehole, the well head control equipment is disconnected through saidsafety joint, or other quick-connect joint, and then lifted by a drillstring to the work deck of the drilling vessel. The guide cableassembly, then in turn, is retrieved either by increasing tension onsaid guide cables to sever a breakable link between the cementedconductor pipe or landing flange and the guide assembly, or byinterconnecting said guide assembly with a portion of a drill string tolift the guide assembly and sever the breakable link to the cementedconductor pipe.

In accordance with another method of carrying out the present invention,the conductor pipe is drilled into the underwater bottom by a concentricdrill string including a plurality of drill collars directly above thebit but below the section of drill string held in tension from the workdeck so that the desired load is applied to the bit when it touchesbottom. In accordance with the invention, no other guiding means is usedto start said well bore in the bottom. The conductor pipe then islowered directly behind said drill string, which opens a pilot hole andthen underreams it to expand the hole to a diameter large enough to letthe conductor pipe pass into the borehole. The landing flange assembledto said pipe limits its depth of penetration; in this method the landingflange and guide assembly are assembled to the conductor pipe and thecomplete unit is lowered from the deck on the guide cables while saiddrill string is still in the well bore maintaining continuity ofconnection between the borehole and the deck.

Further objects and advantages of the present invention, both in themethod of its application to drill a vertical hole into bottom withouttemplates or other guiding means while drilling from a floating vesseland the method of remotely establishing said well head control on bottomfrom the working deck of a drilling vessel will become apparent from thefollowing detailed description of the method and its mode of operationas illustrated by the various forms of apparatus shown in theaccompanying drawings which form an integral part of the presentspecification.

FIG. 1 is a schematic elevation view of one form of apparatus fordrilling into an underwater bottom from a fully floating vessel inaccordance with the method of the present invention;

FIG. 2 is a vertical section of the lower end of the drill stringillustrated in FIG. 1 after the landing flange has been seated on bottomand cementing of the conductor pipe has begun;

FIG. 3 illustrates the lower end of a conductor pipe, including a drillbit attached thereto, at the completion of cementing between the wellbore and the conductor p p FIG. 4 is a vertical view, partly in section,illustrating the positioning of the guide assembly after it slides downthe drill string and engages the conductor pipe in the borehole with thedrill string still connected to the well bore;

FIG. 5 is a vertical view of the underwater Well head or pressurecontrol equipment being lowered along the guide cabels to engage thesafety joint that couples the conductor pipe to said well headequipment;

FIG. 6 illustrates an alternative method for opening a borehole into theunderwater bottom with an independent drill string wherein the conductorpipe and guide assembly are preassembled concentric with said drillstring for lowering therealong into the borehole as a unit and said unitis held suspended below the drilling vessel on guide cables that lowerit to bottom;

FIG. 7 illustrates setting of another surface pipe to be cemented withinthe conductor pipe in the method illustrated in FIG. 6;

FIG. 8 illustrates a preferred method of severing the upper end ofsurface pipe as seen in FIGS. 6 and 7 to permit recovery of the completesafety joint with the well head control equipment when the well bore isto be abandoned.

Referring now to the drawings and in particular FIG. 1, there isillustrated a method of drilling a vertical well bore into an underwaterbottom that may be steeply dipping from a fully floating vessel 10. As afirst step, vessel 10 is suitably positioned and anchored over the drillsite as indicated schematically by anchor lines 11. After the vessel hasbeen positioned on the drill site, there is suspended through a centralwell 12 formed in vessel 10 a drill string 14 that includes an assembledsection of conductor pipe 13. In the arrangement of FIG. 1, conductorpipe 13 is to be cemented in hole 15, but is an integral part of drillstring 14 that also includes drill bit 17, safety joint 19 and anupwardly extending, reduced diameter section 21. Conductor pipe 13 isassembled to a predetermined length depending on the depth of theunconsolidated sediments, identified generally as 23, and the depthneeded to be drilled before a competent formation is found in the solidrock 25. Conductor pipe 13 is likewise selected to have a predeterminedweight that will act as the only weight on bit 17 when the bit firsttouches bottom and irrespective of the depth of water between the vesseland bottom. In open water, vessel 10 will be subjected to periodic riseand fall, as well as pitching and rolling, due to wave and tide action.For this reason, drill pipe 14 includes as an integral part thereof, asplined or sliding sleeve connection 43 that assures that the bit willrest on bottom with only the desired load thereon. In the arrangement ofFIG. 1, drill string 14, including conductor pipe 13, is then supportedby vessel 10 through a conventional derrick .27 that includes book 29,travelling block 31, cable 33 and draw works 35. In drilling, it is tobe noted that templates, pipes or other guide means are not required inaccordance with the invention to start and drill borehole 15 verticallyinto a clipping bottom where the upper end 21 of drill string 14 is heldin tension so that the entire string hangs as a compound pendulum belowrotary table 3-9. Drill bit 17 is rotated on bottom by rotary table 39driven by any suitable power source such as motor 41. Preferably, motor41 is a rotary hydraulic motor so that the motor can be driven throughflexible hydraulic lines with the motor supported on the 6 gimbaledbearings of rotary table 39.. Rotary table 39 is so mounted to permit itto remain level when the vessel pitches and rolls.

For the purpose of indicating the condition when conductor pipe 13 hasbeen drilled to the desired depth, and to limit its penetration, alanding flange 45, formed as either a four-armed spider, or as arelatively flat plate of somewhat enlarged diameter, is clamped to thetop end of conductor pipe 13. Thus, when conductor pipe 13 has beendrilled to the desired depth, the driller Will immediately be notifiedby an increase in torque at the rotary table and/ or by a decrease inthe weight supported by derrick 27 due to part of the weight of uppersection 21 of drill string 14 being supported on flange 45. The drillingof the conductor pipe is desirably accomplished by using sea water as adrilling fluid. In the present arrangement this is illustrated by intakepipe 47 being interconnected to a pump 49 and to drill pipe 14 throughhose 51 and swivel 53. During drilling in with sea water, there is ofcourse no return of the cuttings to vessel 10.

In the arrangement shown in FIGS. 1 to 3, drill bit 17 has an enlargeddiameter and includes a core wiper arm 54 in the center of the bit thatkeeps the hole open through the center of conductor pipe 13.

When the conductor pipe has been drilled to sufiicient depth to enter acompetent formation, landing flange 45 touches bottom as seen in FIG. 2.The hole is then conditioned by continued circulation of sea water sothat the hole is flushed of debris. After conditioning of the hole,cement is supplied by switching connections of valve 57 to pump cementfrom the mixing tank 59 through mud pump 49 and into drill pipe 14through swivel 53 (FIG. 1). As best seen in FIG. 2, cement is clearedfrom conductor pipe 13 by dropping a ball 61 through a side-opening portor kelly cock 63 connected directly below swivel 53. When ball 61 seatson the top of cement chaser 65, pump pressure, as indicated by meter 50,will be increased to release chaser 65 from its seat in coupling 67 inthe drill string lying directly above safety joint 19. Cement chaser 65then cleans cement from the lower end of the conductor pipe as shown inFIG. 3. Core wiper 54 stops the downward travel of cement chaser 65 andprevents back flow of cement 69 from well bore 15 into conductor pipe13. Desirably, enough cement is used so that substantially the entirelength of conductor pipe 13 is cemented in the hole, but not enough isused so that cement balls up over the top of landing flange 45.

Immediately after the conductor pipe has been set in cement, a guideassembly, identified generally as 71, is lowered on a pair of guidecables identified as 73. As seen in FIG. 1, guide assembly 71, initiallyhangs in the well 12 of vessel 10 below the rotary table. Guide assembly71 includes a tubular member or bucket element 75 that gives theassembly substantial weight. The assembly is free to slide down alongdrill pipe 21 and over the outer portion of safety joint 19 when theguide lines are slacked from cable drums 76 on the vessel. When landedadjacent to, or on top of, landing flange 45, as in FIGS. 4 and 5,bucket member 75 is latched to the lower or stationary portion 77 ofsafety joint 19 by a pair of latch members 78 that engage groove 72 inlower member 77. Alternatively, bucket or weight member 75 may latchdirectly to conductor pipe 13 or to landing flange 45 if so desired. Thefunction of latches 78 is to connect guide assembly 71 to the upper endof conductor pipe 13 by sheerable links, such as pins 80. Pins 80 arebreakable .by an upward pull on bucket 75 of a predetermined magnitudethat rotates latches 78 about pivot pins 82. The respective pins 82 passthrough corresponding elongated openings formed through the pivoted endportions of the latch members 78. These openings are disposed to permitthe latches to slide on the pins toward and away from the latchingposition as well as to pivot around the pins. A respective spring biaseseach latch to its latching position. Thus when the bucket member 75 islowered over the portion 77 of the safety joint the radially disposedprojections on the latter displaces the latch members outwardly topermit the bucket assembly to clear such projections until the latchmembers are in alignment with the groove 72. When the bucket assemblyreaches this position the biasing springs force the ends of the latchmembers into engagement with the groove. The groove-engaging end portionof the latch members are notched to form a surface complementary to thatof the upper radially disposed surface of the groove. This provides asecure engagement between the groove and the latches and prevents thelatch members from being displaced radially by normal working stresses,as indicated in FIG. 5. As shown in FIGS. 4 and 5, guide assembly 71 hasa pair of arms 79 that extend radially outward from the center line ofthe borehole to anchor the lower ends of guide cables 73.

As best seen in FIG. 1, guide cables 73 are normally maintained tautbetween bottom and floating vessel 10 by a weight 81 hung on sheaveassembly 83 below cable drum 76. After bucket 75 of guide assembly 71has been latched to conductor pipe 13 and the cement is set, the upperportion or barrel section 85 of safety joint 19 is disconnected so thatupper section 21 of drill pipe 14 can be raised and racked on the drilldeck, ready for further drilling through the lower end of the cementedcasing 13.

At this time, in accordance with the present invention, guide cables 73are slacked off so that conductor pipe 13 is left standing free in thewell bore and supported on flange 45 while the cement sets. Thus, cement69 is not worked by the conductor pipe or pulled up by the guide cableswhile it sets.

After cement 69 has set, conductor pipe 13 is securely anchored in acompetent formation along the well bore. Drilling then proceeds throughthe conductor pipe by drilling up ball 61 and the part of the cement atthe bottom of the borehole. In accordance with the method illustrated byapparatus shown in FIGS. 1 to inclusive, the well head or pressurecontrol equipment is coupled directly to conductor pipe 13 throughsafety joint 19 heretofore forming part of the drilling string. In saidmethod, as illustrated in FIG. 4, the barrel 85 and locking sleeve 86 ofsafety joint 19 are assembled below a well head assembly, identifiedgenerally as 87. While the well head or pressure control assembly willvary in accordance with the pressure conditions that are expected to bemet in drilling ahead, in the present arrangement it comprises a pair ofgate-type blow out preventers (hereinafter called BOPs) 89 and 91assembled in series to the upper end of safety joint barrel 85. In apreferred form of apparatus for carrying out the invention, lower BOP 89includes a pair of shearing rams constructed in accordance with myapplication Ser. No. 556,685, filed Dec. 30, 1955, now Patent No.2,919,111. As disclosed in said application, the opposite sides of thepipe-engaging rams that normally encircle a section of drill pipe,similar to those in BOP 91, as seen in FIG. 5, are provided withshearing bars that override one another. The purpose of these shearingrams is to provide a system, such that if storm or other hazardousoperating conditions require, the drill pipe in the borehole can be cutoff at the well head without requiring each section of the entirestiring to be raised, uncoupled and racked before the hole can beabandoned. Such action is of course drastic in that the entire length ofdrill pipe would need to be recovered if the hole is to be used again;such apparatus provides a method for leaving the hole, but at the sametime maintains full control of well pressures while abandoning theborehole under emergency conditions.

Upper blow out preventer 91 is of conventional design and may eithercompletely close off the well bore, or grasp the sides of the drill pipewhen the opposite rams 90 and 92 are actuated through hydraulic lines93. Similar hydraulic lines 94 permit control of BOP 89 from the deck ofvessel 10.

Immediately below blow out preventer 89, there is provided a mud fill-upline connection identified generally as 95. A valve 97, hydraulicallyoperable through line 96 permits drilling fluid to be added underpressure to the well bore when drill pipe is out of the borehole. Foradditional safety in the operation of well head assembly 87, there isincluded another pressure controlled full hole blow out preventer 99connected directly to and above BOP 91. BOP 99 is operable through lines100. By this arrangement of BOPs 99, 89 and 91, it is possible to holdcontrol of the well even if control of one of said BOPs is lost byaccident.

Above BOP 99, there is positioned a drilling head 101 whose function isto maintain an hydraulic seal around the rotating drill pipe; said drillpipe not only rotates but also reciprocates therein due to rise and fallof vessel 10 due to waves. Drilling head 101 likewise places a backpressure on drilling fluid returning from the borehole around theoutside of drill pipe 21 and forces said drilling fluid to flow back tothe deck of vessel 10 by way of mud return line 103. Control of the backpressure on drilling fluid returns is by a packing locked by hydraulicpressure applied through line 104. The returned drilling fluid of coursecontains the cuttings from the formation being drilled. These can betested by conventional gas and chip analysis methods. As indicated,return mud line 103 is connected through a side-opening flange member105 positioned directly below drilling head 101.

As indicated above, various combinations of blow out preventionequipment, either of the full hole, or drill pipe engaging types may beassembled between the top of the cemented conductor pipe and thedrilling head. However, desirably this entire assembly is made on thedeck of vessel 10 or in the well 12 through the vessel and then loweredon a section of drill pipe 21A, as shown in FIG. 5. In positioning thisequipment through center well 12 of the drilling vessel an upper andlower pair of guide arms, indicated as 107 and 109 respectively,slidably engage the pair of guide cables 73. A spearing section of drillpipe 21A, preferably having a bull nose portion 111, extends downwardlythrough the entire well head assembly 87 and below safety joint barrel85. In lowering assembly 87, rams 90 and 92 of upper BOP 91 are closedaround a recessed collar portion 102 positioned a fixed distance abovebull nose 111.

As indicated schematically in FIG. 5, bull nose 111 is guided alongcables 73 by guide arms 107, 109 so that even with ship 10 rising andfalling in the water, the well head assembly and in particular barrel 35of safety joint 19 is guided over mandrel 77 of safety joint 19 byfunnel 113 above bucket member 75. For this purpose, a funnelarrangement 113 has a suitably enlarged diameter that is formed as anintegral part of guide assembly 71. Thus, with guide cables 73 againdrawn taut, well head assembly 87 slides down said guide cables whilelowered by derrick 27. Through the latching of barrel to mandrel 77 ofsafety joint, or quick connect unit, 19 a positive connection is madebetween the well head assembly and the conductor pipe.

As suggested by FIG. 5, each of the control hoses 93, 94, 95, 96, 100,103 and 104 is connected to the well head assembly before it is loweredto engage the conductor pipe. Preferably, this is also accomplished ondeck, al though it can be performed directly below the surface of thewater as in well 12 in vessel 10. These control lines preferably passover the side of the vessel 10 and are wound on a reel assembly. Intheir assembly, the entire bundle is passed over the side and the lowerend fished up through center well 12 of vessel 10. Thus, the outer endsof each of the hoses may be attached while the assembly is in the wellor on the working deck and above water; then, the entire assembly islowered along guide cable '73.

Drilling now may proceed to any desired depth with full pressure controlover the well bore and with the well head located on the ocean bottom sothat if required, for

safety of vessel or personnel, the well can be abandoned temporarilywithout loss of pressure control in the well. In such abandonmentprocedure, the hoses can be severed and the guide line 73 dropped withonly buoys to mark their location at the ocean surface, and if need be,the drill pipe can be severed in the hole without danger ofcontaminating the ocean Waters or the adjacent beaches.

As best indicated in FIG. 5, after the well head is assembled, the drillbit is assisted in entering and leaving the well head assembly byanother funnel member 117 that is directly connected to upper guide arm107. Funnel 117 and guide arm 107 are secured directly to drilling head101. Additionally, the bit is guided by a collar arrangement, otherwisecalled a bit guide, that surrounds the drill pipe directly above thebit; said bit guide includes a pair of arms that engage and slide downalong the guide cables to assist the bit in entering the drilling head.

There is illustrated in FIG. 6 another method of establishing wellpressure control after drilling into the underwater bottom by the methodof the present invention. In this embodiment, a hole opener bitarrangement, identified generally as 121, including a pilot bit 123first touches and penetrates the bottom to open a relatively small hole.

Pilot bit 123 is then followed by an underreamer bit 125. In this systemof drilling in, a desired length of conductor pipe or casing 127 issupported below the ships center well 12 and is assembled to a landingflange assembly 129 and guide assembly 131, so that entire assembly canbe hung on guide cables 73 by arms 133. As shown in FIG. 6, the guideassembly 131 is secured by links 135 directly to landing flange assembly129, rather than to the conductor pipe, but in the present case flangeassembly 129 is welded to conductor pipe 127. The conductor pipe 127,landing flange assembly 129, and guide assembly 131 are all assembledbelow the rotary table prior to spudding in of the well, and as showndrill string 122 is lowered through conductor pipe 127.

After the borehole has been opened and underreamed to a sufiicientassembled length of conductor pipe 127, said conductor pipe and guideassembly 131 are lowered along the drill string in the same mannerasguide assembly 71 is lowered along drill string 21 in the arrangementofFIGS. 1, 4 and 5. With the conductor pipe set in the well bore and guideassembly 131 connected to the vessel through cables 73, drill string 122can be withdrawn to substitute a cement shoe for bit 121. However, ifdesired said drill string can include a cement shoe so that the drillneed not be re- .moved from the borehole to cement conductor pipe 127 inthe borehole. The conductor pipe is cemented in the .well bore in muchthe same manner as illustrated in FIG. 2. Where a cement tool is used,it is guided into the conductor pipe by a bit guide sliding down theguide cables 73 and into the borehole by funnel is of course added tofill the annular space between the side of the well bore and theconductor pipe. Desirably, only enough cement is added at this stage sothat the cement does not rise to the top of the conductor pipe as shownin FIG. 7. As will be explained later in connection with FIG. 7, thispermits ports 141 in landing flange 129 to act as cement openings whenanother pipe or liner 143 is cemented within conductor pipe 127.

In accordance with the method disclosed in the arrangement of FIGS. 6, 7and 8, the well bore is drilled to a greater depth before setting ofblow out preventers or other well head control means. Such an operationis usu ally undertaken when a knowledge of the geology of the underwaterbottom indicates that gas and oil under pressure will not be encounteredduring the first few hundred feet of drilling. Accordingly, drilling canproceed through through the bottom of cemented conductor pipe 127, afterthat pipe is set to prevent debris or unconsolidated sediments fromsloughing into the boreholerIn practice, the

depth and diameter to receive the pre- 137. Sufficient cement end ofsurface pipe conductor pipe will be set to a depth of about 50 to 75feet, the depth of surface casing 143 may be of the order of 300 feet,and usually is deep enough so that a competent formation, such as athick bed of impervious shale or other non-porous rock is encountered bythe borehole. By going deeper into the earth before cementing surfacecasing 143, a much greater depth and higher pressures can be withstoodby the pressure control equipment without danger of high pressure oiland gas accumulations blowing out.

There is illustrated in FIG. 7 a preferred method of assembling the blowout prevention equipment, as well as the preferred method of cementingthe surface easing into the deepened well bore. As there shown, surfacecasing 143 extends downwardly to about 300 feet and is run into the wellthrough conductor pipe 127. The upper 143 preferably includes a cementsleeve 145 that extends axially along the upper end of surface casing143. Sleeve 145 is tapered at its lower end 147 so that it can be sealedby welding to the outer surface of the surface casing. The upper end ofsleeve 145 frictionally engages coupling 149 on the mandrel 277 of asafety joint 219. The purpose of cement sleeve 147, as best seen in FIG.7 is to permit the upper end of surface casing 143. Sleeve 145' istapered at its lower 127, but to leave an annular space 159 that willnot be filled with cement.

As further distinguished from the arrangement of FIGS. 4 and 5, aconically tapered portion of mandrel 277 of safety joint 2.19 seatswithin a conical section 157 of landing flange 129 that serves as atubing hanger for surface casing 143. In this way, casing 143 issupported throughout its length until it is cemented into the well boreas illustrated in FIG. 7. In the present embodiment, surface pipe 143 ishung in the well bore on safety joint 219 so that the drill stringthereabove can be disconnected after cement has been set through cementshoe 151 at the lower end of pipe 143. Pipe 143 is guided into the holeby bit guide 221 that will pass the barrel of safety joint 219 to let itrest above guide arms 133 of guide assembly 131. The upper end ofmandrel 277 is sealed against cement by O-rings 161.

Deep drilling is then possible under full pressure control by landingwell head equipment, identical to that of FIG. 5, on safety joint 219.This couples the blow out preventers and the drilling head to axiallycemented section of surface casing 143. After the desired depth isdrilled, it may be desirable to abandon the well bore. When it isdesired to leave the well, the surface casing will normally be left inthe well bore with cement spotted therein to prevent any possible blowout from the borehole. Then, the entire assembly of Well head equipmentis recovered by severing the upper portion of surface casing 143opposite annular section 159 between cement sleeve 145 and the casing.FIG. 8 represents a preferred manner of severing casing 143 with ashaped explosive charge. The tubing can also be cut by a milling cutterrun into the casing. Upon severance of the upper end of casing 143, thecomplete safety joint 219 and the well head equipment secured theretocan be withdrawn from within flange 129. After release of the well headequipment, the guide assembly 131 can also be recovered in much the samemanner as that illustrated in FIGS. 4 and 5. That is, the lines orcables 73 can be tightened to sever pins 163 that hold links 135 toflange 129. Desirably, guide assembly 131 is pulled free from landingflange 129 by a special tool run into guide assembly 131 on a drillstring. As indicated in FIG. 8, weight or bucket element 165 of theguide assembly has a pair of diametrically op- 'posed J-slots 167 formedin its upper, inner surface. Slots 167 can be engaged by the liftingtool so that the drill derrick hoist can apply the necessary force toshear pins 163. In this way, only the cemented casing and landing flange129 are left on bottom.

Where only a single pipe is cemented in the well bore, as in theapparatus shown in FIGS. 1 to 5, the conductor pipe also desirably has acement sleeve surrounding its upper end. This is best seen in FIG. 5,where the details of the connection between safety joint 19 andconductor pipe 13 are shown in vertical section. In this arrangementsleeve 88 is welded to conductor 13 at its lower end and slips over thelower coupling end of mandrel 77 of safety joint 19. In this embodiment,severance of conductor 19 within the cement sleeve allows recovery oflanding plate 45 as well as safety joint 19.

In the foregoing detailed description of two forms of apparatus forcarrying out the method of the present invention, it will be apparentthat various modifications and changes can be made in both said methodand the apparatus without departing from the present invention.Accordingly, all such modifications and changes falling with in thescope of the appended claims are intended to be included therein.

I claim:

1. The method of drilling and working in a well bore in an underwaterbottom from a floating vessel which comprises positioning said vesselover an underwater drilling site, suspending an assembled conductor pipeof a predetermined length from said vessel and above the underwaterbottom, connecting a landing flange to the upper end of said conductorpipe, assembling in axial alignment with and as an integral part of saidconductor pipe and landing flange assembly a tubular guide assemblyhaving aflixed thereto at least a pair of guide cables, inserting adrill string with a radially expandable and contractible drill bitattached to the lower end thereof axially through said conductor pipefrom said vessel and into contact with said underwater bottom, radiallyexpanding said drill bit to a diameter greater than that of saidconductor pipe and rotating said drill string by means on said vesselwhile lowering said drill string from said vessel to drill into saidunderwater bottom a bore hole having a diameter and depth to permit saidconductor pipe to be received therein to permit said landing flange toseat on said underwater bottom, lowering said conductor pipe, saidlanding flange and said guide assembly from said vessel along said drillstring and guiding said conductor pipe into said bore hole with saiddrill string to position said landing flange on said underwater bottom,radially contracting said drill bit to a diameter smaller than that ofsaid conductor pipe and retracting said drill string and said drill bitfrom said conductor pipe while maintaining a flexible connection betweensaid conductor pipe and said vessel with said guide cables, loweringfrom said vessel along said guide cables and to said tubular guideassembly a string of cement tubing having a guide member attachedthereto and cooperating with said guide cables, guiding the lower end ofsaid string of cement tubing into said conductor pipe by said guidecables and said tubular guide assembly, introducing cement from saidvessel through said string of cement tubing into said bore hole andcementing said conductor pipe in said bore hole, retracting said stringof cement tubing from said conductor pipe and slacking said guideca'bles while said cement sets.

2,. The method of drilling and working in a submerged well from afloating vessel which comprises anchoring a floating drilling vesselabove a submerged well site on an underwater bottom, suspending a drillstring from a working platform of said vessel, said drill stringincluding a radially expandable and contractible drill bit aflixed tothe lower end thereof and rotatable by power transmitted thereto by saiddrill string, assembling a conductor pipe concentric with said drillstring, securing a half part ofan automatically engaging connector toand concentric with the upper end of said conductor pipe, suspendingsaid conductor pipe from said working platform on at least a pair ofcables so that the lower end of said conductor pipe is above theunderwater bottom to be drilled into by said drill bit, lowering saiddrill string into contact with said underwater bottom, radiallyexpanding'said drill bit to a diameter greater than that of saidconductor pipe and rotating said drill bit while lowering said drillstring from said working platform to drill a bore hole into saidunderwater bottom of a diameter and to a depth to permit said conductorpipe to be inserted therein with the upper end of said conductor pipe'held adjacent said underwater bottom by a landing flange securedthereto and contacting the said underwater bottom, lowering saidconcentric conductor pipe along said drill string by means of saidcables and guiding the lower end of said conductor pipe into said borehole with said drill string, lowering said conductor pipe into said borehole by means of said cables to land said landing flange on saidunderwater bottom, introducing cement into said bore hole through saiddrill string and forcing said cement between the outer wall of saidconductor pipe and the wall of said bore hole, radially contracting saiddrill bit to a diameter smaller than that of said conductor pipe andwithdrawing said drill bit and drill string from said conductor pipe,slacking said cables while said cement sets, retightening said cablesand lowering from said working platform blowout prevention equipmentadapted to receive a drill string in fluid-tight slidable relationshipand having the other half part of said automatically engaging connectorsecured to and extending from the bottom thereof and having a guidemember attached thereto and co-operating with said cables along saidcables and into contact with the upper portion of said conductor pipe,afiixing said blowout prevention equipment to the upper portion of saidconductor pipe by said automatically engaging connector to provide aseal between the upper end of said conductor pipe and a drill stringpassing through said blowout prevention equipment.

3. The method of drilling and working in a submerged well from afloating vessel which comprises anchoring a floating drilling vesselabove a submerged well site on an underwater bottom, suspending a drillstring from a working deck of said vessel, said drill string including aradially expandable and contractible drill bit afiixed to the lower endthereof and rotatable by power transmitted thereto by said drill string,assembling a conductor pipe concentric with said drill string, securinga half part of an automatically engaging connector to and concentricwith the upper end of said conductor pipe, suspending said conductorpipe from said working deck on at least a pair of cables so that thelower end of said conductor pipe is above the underwater bottom to bedrilled into by said drill bit, lowering said drill string into contactwith said underwater bottom, radially expanding said drill bit to adiameter greater than that of said conductor pipe and rotating saiddrill bit while lowering said drill string from said working deck todrill a bore hole into said under-water bottom of a diameter and to adepth to permit said conductor pipe to be inserted therein with theupper end of said conductor pipe held adjacent said underwater bottom bya landing flange secured thereto and contacting the said underwaterbottom, lowering said concentric conductor pipe along said drill stringby means of said cables and guiding the lower end of said conductor pipeinto said bore hole with said drill string, lowering said conductor pipeinto said bore hole by means of said cables to land said landing flangeon said underwater bottom, radially contracting said drill bit to adiameter smaller than that of said conductor pipe and withdrawing saiddrill bit and drill string from said conductor pipe, lowering from saidworking deck along said guide cables and to said upper end of saidconductor pipe a string of cement tubing having a guide member attachedthereto and co-operating with said cables, guiding the lower end of saidstring of cement tubing into said conductor pipe by said guide cables,introducing cement from said working deck through said string of cementtubing and cementing said conductor pipe in said bore hole, retractingsaid string of cement tubing from said conductor pipe and slacking saidcables while said cement sets, retightening said cables and loweringfrom said working deck blowout prevention equipment adapted to receive adrill string in fluid-tight slidable relationship and having the otherhalf part of said automatically engaging connector secured to andextending from the bottom thereof and having a guide member attachedthereto and co-operating with said cables along said cables and intocontact With the upper portion of said conductor pipe, aflixing saidblowout prevention equipment to the upper portion of said conductor pipeby said automatically engaging connector to provide a seal between theupper end of said conductor pipe and a drill string passing through saidblowout prevention equipment.

References Cited UNITED STATES PATENTS Smith.

Wigle 166-27 X Kinniear 16627 McNeill 2552.5 Bauer et al. 255-2.5 Baueret al 175-7 10 CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, WALTER BISLOWITZ, HAR- RISON R. MOSELEY, Examiners.

15 R. E. FAVREAU, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,341,398 September 12, 1967 Kingsley M. Nicolson ears in the abovenumbered pat- It is hereby certified that error app d Letters Patentshould read as ent requiring correction and that the sai correctedbelow.

Column 5, line 18, for "cabels" read cables column 7, line 61, for"stiring" read string column 9, line 73, strike out "through"; column10, line 25, for "143. Sleeve 145 is tapered at its lower" read 143 tobe cemented into conductor pipe Signed and sealed this 3rd day ofDecember 1968.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

1. THE METHOD OF DRILLING AND WORKING IN A WELL BORE IN AN UNDERWATERBOTTOM FROM A FLOATING VESSEL WHICH COMPRISES POSITIONING SAID VESSELOVER AN UNDERWATER DRILLING SITE, SUSPENDING AN ASSEMBLED CONDUCTOR PIPEOF A PREDETERMINED LENGTH FROM SAID VESSEL AND ABOVE THE UNDERWATERBOTTOM, CONNECTING A LANDING FLANGE TO THE UPPER END OF SAID CONDUCTORPIPE, ASSEMBLING IN AXIAL ALIGNMENT WITH AND AS AN INTEGRAL PART OF SAIDCONDUCTOR PIPE AND LANDING FLANGE ASSEMBLY A TUBULAR GUIDE ASSEMBLYHAVING AFFIXED THERETO AT LEAST A PAIR OF GUIDE CABLES, INSERTING ADRILL STRING WITH A RADIALLY EXPANDABLE AND CONTRACTIBLE DRILL BITATTACHED TO THE LOWER END THEREOF AXIALLY THROUGH SAID CONDUCTOR PIPEFROM SAID VESSEL AND INTO CONTACT WITH SAID UNDERWATER BOTTOM, RADIALLYEXPANDING SAID DRILL BIT TO A DIAMETER GREATER THAN THAT OF SAIDCONDUCTOR PIPE AND ROTATING SAID DRILL STRING BY MEANS ON SAID VESSELWHILE LOWERING SAID DRILL STRING FROM SAID VESSEL TO DRILL INTO SAIDUNDERWATER BOTTOM A BORE HOLE HAVING A DIAMETER AND DEPTH TO PERMIT SAIDCONDUCTOR PIPE TO BE RECEIVED THEREIN TO PERMIT SAID LANDING FLANGE TOSET ON SAID UNDERWATER BOTTOM, LOWERING SAID CONDUCTOR PIPE, SAIDLANDING FLANGE AND SAID GUIDE ASSEMBLY FROM SAID VESSEL ALONG SAID DRILLSTRING AND GUIDING SAID CONDUCTOR PIPE INTO SAID BORE HOLE WITH SAIDDRILL STRING TO POSITION SAID LANDING FLANGE ON SAID UNDERWATER BOTTOM,RADIALLY CONTRACTING SAID DRILL BIT TO A DIAMETER SMALLER THAN THAT OFSAID CONDUCTOR PIPE AND RETRACTING SAID DRILL STRING AND SAID DRILL BITFROM SAID CONDUCTOR PIPE WHILE MAINTAINING A FLEXIBLE CONNECTION BETWEENSAID CONDUCTOR PIPE AND SAID VESSEL WITH SAID GUIDE CABLES, LOWERINGFROM SAID VESSEL ALONG SAID GUIDE CABLES AND TO SAID TUBULAR GUIDEASSEMBLY A STRING OF CEMENT TUBING HAVING A GUIDE MEMBER ATTACHEDTHERETO AND COOPERATING WITH SAID GUIDE CABLES, GUIDING THE LOWER END OFSAID STRING OF CEMENT TUBING INTO SAID CONDUCTOR PIPE BY SAID GUIDECABLES AND SAID TUBULAR GUIDE ASSEMBLY, INTRODUCING CEMENT FROM SAIDVESSEL THROUGH SAID STRING OF CEMENT TUBING INTO SAID BORE HOLE ANDCEMENTING SAID CONDUCTOR PIPE IN SAID BORE HOLE, RETRACTING SAID STRINGOF CEMENT TUBING FROM SAID CONDUCTOR PIPE AND SLACKING SAID GUIDE CABLESWHILE SAID CEMENT SETS.